Safety device for railroad operation



Feb. 10, 1931. F. SCHROETER ET AL 1,791,938

SAFETY DEVICE FOR RAILROAD OPERATION Filed Nov. 16. 1929 FRlTZ SCHROETERAND BY FRIT MICHELE NY ATTORNEY Patented Feb. 10, 1931 UNITED STATESPATENT OFFICE FRITZ SCHROETER AND FRITZ MIGHELSSEN, OF BERLIN, GERMANY,ASSIGNORS TO TELEFUNKEN GESELLSCHAFT FOR DRAHTLOSE TELEGRAPHIE M. B. IL,BER- LIN, GERMANY, A CORPORATION OF GERMANY SAFETY DEVICE FOR RAILROADOPERATION Application filed November 18, 1929, Serial No. 407,649, andin Germany November 27, 1928.

This invention relates generally to improvements in railway signallingsystems and more particularly to a railway signalling system whichutilizes infra-red rays.

It is known in the prior art that the presence of infra-red rays may bedetected by certain sensitive devices which react to the modulatedfrequencies of transmitted infra-red rays. The modulation of infra-redrays may be effected either in a mechanical way (e. g. by periodicshutting) or by electrical means. In order to modulate properly theinfra-red radiation of incandescent lamps by way of rhythmic variationsof the feed current it is necessary, as demonstrated by tests, to use afilament wire which is very thin and is able to burn in an atmosphere ofhydrogen. The filament may be of a loop or zig-zag structure. It isknown that infra-red rays may be directed exactly and furthermore thatthey can be completely separated from the visible part of the radianceof the transmitter by suitable filters. In addition infra-red rayspossess the faculty of penetrating fog which fre- 2 quently prevents therecognition of optical signals. The devices for the establishment ofinfra-red rays are based on the influence which they exert on certainelectrical properties of the indicators; thus it becomes possible toapply the modern amplifying technique.

The present invention makes use of this and other qualities of theinfra-red waves for a new safety device on railroads which is obviouslyapplicable also for subways and for street traflic regulation. Therailroads use for the regulation of train sequence and for the purposeof preventing accidents, collisions, derailments etc., optical signallamps of various colors which consist of advance signals and mainsignals and signify, according to their color, either go ahead or stop.

In daylight these signals are transmitted in the form of differentsemaphore positions.

This method of signalling is, however, ineffective in a fog. It isfurthermore a fact that even with good visibility there is a danger ofthe signals not being seen on account of failure or inattention of theengine crew. The main purpose of this invention is to supplement orreplace the various existing visible signals by invisible signals ofdirected infrared transmitters with various modulating frequencies. Forinstance, a modulating frequency of 50 cycles may signify go ahead and afrequency of 25 cycles may denote step. A separate infra-red transmittermay, of course. be provided for every signal but it is equally possibleto modulate one single transmitter in accordance with the varioussignals. As compared to o tical signals these infra-red signals havetile advantage of a long range of action with a small expenditure ofenergy. The advance signals heretofore necessary may thereforeeventually be dispensed with. Besides being invisible, these infra-redsignals do not confuse the engine crew, as there is no possibility ofmistaking them for other optical signals which may exist. Furthermore,the infrared signals remain operative in a fog which would render theoptical signals ineffective.

The receiving arrangement in the locomotive consists of infra-redindicators which permit the recording of the various modulatingfrequencies. The latter may, if necessary, be amplified by electricalmeans and filtered out by suitable electrical or mechanical resonancesystems.

The single figure of the drawing shows by way of example one embodimentof the invention.

In said figure, 1 illustrates a parabolic reflector with a source ofinfra-red rays 2 at its focus. The infra-red rays may be modulated inany well known manner by a frequency of 50 cycles and 25 cycles tocorrespond to the conditions of the track by the presence or absence ofa train on the particular block in question. On each train will belocated a parabolic reflector 3 arranged in such a position that lightfrom the track signal reflector 1 willbe foeussed toward parabolireflector 3. At the focus of reflector 3 any suitable detecting devicemay be employed such as a platinum wire 4 whose resistance changes inaccordance with infra-red rays. The change of resistance of 4 will inturn vary the current flowing around circuit 10 made up of resistance 4,battery 5 and primary winding 6 of transformer 11. The secondary 7 oftransformer 11 is connected to the input of an amplifier 8 which may becomprised of a triode, the output of which may be connected to certaintuned relays not shown for the purpose of indicating the signaltransmitted by source 2.

It is evident that the resistance of circuit 10 changes in accordance tothe modulations produced at 2 so that the grid of tube 8 being directlydependent thereon will in turn transn'iit the modulation frequency tothe output circuit 9 with the result that the properly tuned relay willrespond.

The advantage of receiving modulated infra-red waves consists in theelimination of interference from other sources of infra-red rays such asthe sun, blast furnaces etc. These sources are capable of causing only asteady current to flow in the receiver which can be eliminated byelectrical circuit elements. The reading or detection of these signalsmay be effected in various ways. The signals may be communicated to thecrew by means of their variations in pitch. It is also feasible toconnect the receiver to a device which contains glow-discharge orincandescent lamps in the usual colors of the railroad signals, thecircuit being arranged in such a manner that every time a lamp flashesup, of the color which corresponds to the modulation frequency of theinfra-red assigned to the color in question. Inasmuch as the infra-redrays possess a long range of action the signal becomes perceptible tothe engine crew earlier than with the present devices. To eliminate thedanger of the crew not heeding the signal this invention may be arrangedso as to automatically operate the controlling levers of the locomotivein any well known manner. It is, for instance, feasible to actuate bymeans of electrical or mechanical resonators different relays for thedifferent signals, the relays being made to control the locomotive bymagnetic forces. It is of course possible to radiate the variousmodulation frequencies with light serving as a carrier frequency. Inthis case sensitized cells are employed on the locomotive. By theapplication of suitable filters the radiators, that is, the transmittersmay be made to radiate the colored lights as well as the infra-redwaves. The radiators may thus serve the double purpose of being opticalsignals as well as transmitters of the various modulated frequencies ofthe infra-red waves.

Claims:

1. In a railway signalling system having a signal emitter adapted toemit desired signals by means of infra-red rays, a receiver on a traincomprising in combination an infra-red ray responsive device and anamplifier coupled thereto.

2. In a railway signalling system having a signal emitter adapted toemit desired signals by means of infra-red rays, a receiver on a traincomprising in combination an inframamas red ray responsive device, anamplifying circuit comprising a space discharge device having an inputand an output circuit, said input circuit bein connected to saidinfra-red ray responsive evice and a tuned relay system connected tosaid output circuit.

3. In a railway signalling system having a signal emitter adapted toemit desired signals by means of modulated infra-red. rays, eachdifl'erent signal to be transmitted being distinguished by modulatingthe infra-red ray with a particular frequency, a receiver on a traincomprising in combination an infrared ray responsive device, anamplifier coupled thereto and a tuned relay system adapted todistinguish and segregate the received signals.

FRITZ SCHROETER. FRITZ MICHELSSEN.

